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Python Coding
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Write real Python in the browser. Instant feedback. From beginner to expert.

467 challenges 330 easy 120 medium 17 hard

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All Python Basics Strings & Text Lists & Arrays Dicts & Sets Functions & Closures OOP & Classes Data Structures & Algorithms Advanced Python Iterators & Generators Decorators & Context Managers Error Handling & Exceptions Regular Expressions Math & Number Theory Bit Manipulation Dynamic Programming Trees & Binary Trees Graphs & Graph Algorithms Recursion & Backtracking Greedy Algorithms Binary Search Two Pointers & Sliding Window Stacks & Queues Heaps & Priority Queues Linked Lists Matrix & 2D Arrays Datetime & Time Calculations Data Formats & Parsing SQL & SQLite Numpy & Vectorized Computing Cryptography & Hashing

Two Pointers & Sliding Window hard

Trapping Rain Water

Given an array of non-negative integers representing an elevation map, compute how much water it can trap after raining.

array two-pointers water-trapping

Two Pointers & Sliding Window hard

Minimum Window Substring

Implement a sliding window algorithm to find the minimum window substring containing all characters of a given pattern.

sliding-window two-pointers strings

Two Pointers & Sliding Window hard

Subarrays with K different ints

Count the number of contiguous subarrays that contain exactly K distinct integers.

sliding-window two-pointers hashmap

Showing 3 challenges · hard

Guide: free Python coding challenges

Practice Python by solving problems

PythonSkillset challenges are hands-on coding exercises from beginner to advanced. Open a challenge, read the problem, write Python in the split-pane editor, and run tests with Pyodide — no install required.

How to use the arena

Pick a category — basics, algorithms, strings, and more
Open a challenge, read the statement, and edit the starter code
Run tests, fix failures, then try a related quiz or tutorial lesson

Challenges vs tutorials and quizzes

Challenges test what you can build under constraints. For guided teaching, use our Python tutorials. For quick checks, try quizzes or copy snippets from code samples.